The present invention relates to a buckle for a watch band, and more particularly to a buckle having a lock mechanism and a pair of push plates for releasing the locking of the buckle by the lock mechanism.
Japanese Utility Model Application Laid-open No. 4-54215 discloses a buckle for a watch band. FIGS. 10 to 12 show the buckle. The buckle comprises an engaging member 20 and a rotatable clasping member 21 rotatably mounted on an end of the engaging member 20. The engaging member 20 comprises a frame member 26, a first operating member 22 as a lock lever, and a second operating member 23 as a pressing-up lever. The rotatable clasping member 21 comprises a cover plate 24 rotatably engaged with the frame member 26, and an engaging plate 25 projecting from the underside of the cover plate. The engaging plate 25 comprises a downward slant 25a, a hook portion 25b and a spherical projection 25c.
As shown in FIG. 11, the first and second operating members 22 and 23 are slidably mounted in the frame member 26 so as to be moved in the lateral direction with respect to the longitudinal direction of the band (not shown), and outwardly urged by a spring 28. Two stopper pins 26b are provided, each of which is slidably engaged with a slit of the operating member 22 (23) so as to prevent the member from removing from the frame member 26. The inner end portions of the first and second operating members are partially overlapped with each other. The first operating member 22 has a lock portion 22a. The second operating member 23 has an upward slant 23a as a pressing-up slant to be abutted on the downward slant 25a of the engaging plate 25.
Referring to FIG. 10, a connecting link 27 having an engaging rod 29 is connected to another band (not shown).
Method of coupling the buckle is as follows.
The cover plate 24 is inserted into an opening behind the engaging rod 29 of the connecting link 27, and is rotated about a connecting portion 24a. The engaging plate 25 is inserted into an opening 26a of the frame member 26. The downward slant 25a of the engaging plate 25 engages with the locking portion 22a of the first operation member 22 so that the operating member 22 is inwardly moved. When the slant 25a passes the lock portion 22a, the operating member 22 is returned to the home position by the elastic force of the spring 28. Thus, the lock portion 22a engages with the hook portion 25b.
In operation for disengaging the buckle, the operating members 22 and 23 are pushed at the same time to release the lock portion 22a from the hook portion 25b, while the upward slant 23a of the second operating member 23 pushes the downward slant 25a of the engaging plate upward, so that the cover plate 24 is pushed up. The released cover plate 24 is rotated about the connecting portion 24a and removed from the connecting link 27.
In such a buckle, the cover plate must be rotated by fingers in order to release it from the engaging member 20. In other words, the releasing operation is complicated.
On the other hand, it may occur that the cover plate 24 is accidentally released, if the operating members 22 is pushed. In order to prevent the accident, the spherical projection 25c is provided on the engaging plate 25 as an additional locking structure. The projection 25c is adapted to abut on the periphery of the opening 26a when the hook portion 25b engages with the lock portion 22a. Thus, the cover plate 24 is prevented from releasing. In such a device, it is necessary to ensure a constant engaging force of the projection 25c against the periphery of the opening 26a. However, the projection 25c wears with time to reduce the engaging force, which may cause the releasing of the cover plate.